Purification of metal-organic framework materials

ABSTRACT

A method of purification of a solid mixture of a metal-organic framework (MOF) material and an unwanted second material by disposing the solid mixture in a liquid separation medium having a density that lies between those of the wanted MOF material and the unwanted material, whereby the solid mixture separates by density differences into a fraction of wanted MOF material and another fraction of unwanted material. 
     15

This application claims benefits and priority of U.S. provisionalapplication Ser. No. 61/210,980 filed Mar. 25, 2009, the disclosure ofwhich is incorporated herein by reference.

CONTRACTUAL ORIGIN OF THE INVENTION

The invention was made with government support under Grant No.DE-FG02-01ER15244 awarded by the Department of Energy. The Governmenthas rights in the invention.

FIELD OF THE INVENTION

The present invention relates to a method of purification of a crude(contaminated) metal-organic framework material that includes anotherunwanted material, which may be another metal-organic framework materialor other unwanted material.

BACKGROUND OF THE INVENTION

A tremendous development in the area of functional, nanostructuredmaterials is the emergence of large numbers of structurally welldefined, permanently microporous metal-organic framework materials(MOFs). Consisting of metal-ion or -cluster nodes and multi-topicorganic struts, such materials are often characterized by very largeinternal surface areas, low densities, and uniformly sized channels andpores.¹ Among the many applications that may capitalize on theseextraordinary properties are gas storage,² chemical separations,³ andselective catalysis⁴.

MOFs are generally synthesized via one-pot solvothermal methods. Sincepurification of the resulting network solids is not feasible via themethods usually employed by chemists (distillation, recrystallization,chromatography, sublimation, etc.), a premium is placed on discoveringconditions that yield pure products. Typically, discovery entailssystematically evaluating scores of reaction conditions that differ onlyslightly from initial or refined conditions (e.g. temperature, solventcomposition, reactant concentrations, reaction time, and even reactionvessel size). Alternatively, if sufficiently large crystals of distinctmorphology or color are obtained, they can be manually separated fromundesired byproducts—albeit, often in painstaking fashion. Nevertheless,isolation of pure MOF materials is essential; closely structurallyrelated porous materials can often differ enormously in terms ofproperties and functional behavior.⁵ Density separation has occasionallybeen used to isolate molecular metal complexes, but it is not welldeveloped for metal-organic framework chemistry.⁶ References 1-6 are setforth below in the Reference list.

SUMMARY OF THE INVENTION

The present invention relates to a method of purification of a solidmixture of a metal-organic framework material and an unwanted secondmaterial, which may be another metal-organic framework material. Thepresent invention envisions disposing a solid mixture containing awanted or desired MOF material to be isolated and an unwanted materialin a liquid separation medium, such as an organic solvent, having adensity that lies between those of the wanted MOF material and theunwanted material, whereby the solid mixture separates by densitydifferences into a fraction of wanted MOF material and a fraction ofunwanted material.

The present invention also envisions disposing a solid mixturecontaining a wanted MOF material to be isolated and an unwanted secondmaterial in a first liquid separation medium, such as a first organicsolvent, having a density greater than that of the wanted MOF materialand introducing a second liquid separation medium, such as a secondorganic solvent miscible in the first separation liquid, having a lesserdensity in a manner to adjust the collective density of the separationliquid so that it lies between those of the wanted MOF material and theunwanted material, whereby the solid mixture separates into a floatingfraction of the wanted MOF material and a sinking fraction of theunwanted material.

The present invention is advantageous for rapidly purifying an MOFmaterial and its applicability for use for three problems commonlyencountered in purifying an MOF material: 1) isolation of a desiredcrystalline MOF material from a solid mixture containing a secondcompound comprising the same organic-strut and/or metal-ion buildingblocks, 2) separation of a desired mixed-organic strut material from asecond crystalline MOF material containing only a single type of organicstrut, and 3) separation of a non-interpenetrating MOF material from anotherwise identical material consisting of catenated networks. Themethod is not limited to these uses and may be practiced to purify MOFmaterials vis-à-vis other materials including, but not limited to,linear coordination polymers or insoluble metal salts.

Other advantages of the present invention will become apparent from thefollowing detailed description taken with the following drawings.

BREIF DESCRIPTION OF THE DRAWINGS

FIG. 1 includes representations of structures of organic struts andMOFs. 1: 4,4′,4″-s-triazine-2,4,6-triyltribenzoate (TATB);2:1,4-naphthalenedicarboxylate (NDC); 3:N,N′-di-(5-aminoquinoline)-1,4,5,8-naphthalenetetracarboxydiimide(diQuNI); 4: 4,4′-biphenyldicarboxylic acid (BPDC). 5-7: are describedbelow in specification. Zn(II) ions shown as tetrahedra functioning asmetal-ion building blocks. For clarity, interwoven networks are omitted.

FIG. 2A is a powder x-ray diffraction for example 1. Structure 5simulation (bottom plot), 5 after separation (middle plot), and greenneedle impurities (top plot). FIG. 2B represents a vial after separationwas achieved with teal-colored crystals of MOF material (A) as aseparate top separate floating layer and green needle impurities (B) asa bottom separate sinking layer.

FIG. 3 is a powder x-ray diffraction for example 2. Structure 6simulation (bottom plot), 6 after purification (middle plot) and whiteimpurities (top plot).

FIG. 4A is a powder x-ray diffraction for example 3. 7 a simulation(bottom plot), 7 a after purification (middle plot) and 7 b (top plot).Material 7 is 7 a. The asterisk * indicates that the peak intensity isreduced by 80% in order to elucidate the rest of the spectrum. FIG. 4Brepresents a vial after separation was achieved with IRMOF-10 (A′)floating as a separate upper layer while IRMOF-9 (B′) sinking as aseparate layer.

FIG. 5 is a diagrammatic view of H₂bpdc and L reacted with Zn(NO₃)₂ ofExample 4 to synthesize a catalytically active MOF material (A) and anon-reactive MOF species (B).

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method of purification of a solidmixture of a metal-organic framework (MOF) material and an unwantedsecond material, which may be another metal-organic framework materialwith a different framework structure and/or morphology. An illustrativeembodiment of the invention involves disposing the solid mixturecontaining the wanted MOF material to be isolated and the unwantedmaterial in a liquid separation medium, such as an organic solvent,having a density that lies between those of the wanted MOF material andthe unwanted material, whereby the solid mixture separates by densitydifferences into a fraction of wanted MOF material and a fraction ofunwanted material. The method is both straightforward and broadlyapplicable. The method of the present invention can be used to isolateeven minor components (e.g. 15%) of mixed solid materials (phases,compounds, and the like).

In another illustrative embodiment, the present invention envisionsdisposing a solid mixture in a first separation liquid, such as anorganic solvent, having a density greater than that of the wanted MOFmaterial so that it will float on the first liquid separation medium andthen and introducing a second liquid separation medium, such as anotherorganic solvent miscible in the first separation liquid, having adensity less than that of the first liquid separation medium in a mannerto adjust the collective density of the collective liquid separationmedium (the separation medium having the first and second miscibleseparation liquids) so that it lies between those of the wanted MOFmaterial and the unwanted material, whereby the solid mixture separatesinto a floating fraction of wanted MOF material and a sinking fractionof unwanted material.

The present invention can be practiced to purify a crude (contaminated)solid mixture that, as synthesized, contains a wanted MOF to be isolatedand an unwanted second material, which may be another metal-organicframework material or other contaminate material. For example, thepresent invention envisions purifying the crude solid mixture in amanner to 1) isolate a desired crystalline MOF from a mixture containinga second compound comprising the same organic-strut and/or metal-ionbuilding blocks (e.g. Zn(II) ions as tetrahedra), 2) separate a desiredmixed-organic strut material from a second crystalline MOF containingonly a single type of organic strut, and 3) separate anon-interpenetrating MOF from an otherwise identical material consistingof catenated networks. The method is not limited to these uses and maybe practiced to purify MOF materials vis-à-vis other materialsincluding, but not limited to, linear coordination polymers or insolublemetal salts.

In an illustrative embodiment of the invention, CH₂BrCl can be used asthe first or parent solvent (first separation liquid) because of itshigh density (1.99 g/cm³) relative to most MOFs. Starting with a densefirst or parent solvent allows the synthesized crude MOF mixture tofloat. Subsequently, a second miscible but lighter solvent is addeduntil the appropriate density is reached and the solid mixture separatesinto floating and sinking fractions. Powder x-ray diffraction (PXRD)data can then be obtained for both fractions and afterward compared tocandidate simulated PXRD patterns. This procedure should be completedquickly, i.e. before significant solvent exchange with the porous MOFtakes place. Once a solvent of appropriate density is obtained, MOFmaterial separation typically occurs within a few tens of seconds orless.

The following Examples are offered to further illustrate but not limitthe invention:

EXAMPLE 1

The two-fold interpenetrated MOF, Cu₃(TATB)₂(H₂O)₃ (5), was obtained byreacting Cu(NO)₂.3H₂O with 1 in DMSO at 120° C. as described by Sun etal⁷, the teachings of which are incorporated herein by reference Whilecapable of yielding pure 5 (diamond shaped teal crystals), the methodalso sometimes produced a mixture of 5 and a second phase consisting ofcrystalline green needles that analyzed for twice the Cu content of 5.For example, twenty nominally identical reactions were run. Threesamples yielded the desired MOF in pure form, five samples yielded brownamorphous material, and the twelve samples produced a combination of thetwo crystalline materials in a range of ratios. The solid mixture ofcrystalline compounds was purified by: a) sonicating, b) filtering, c)washing with DMSO, and d) depositing the solid mixture in a conventionalseparation funnel, followed by addition of 1:5 (v:v) DMSO:CH₂BrCl(liquid separation medium) pursuant to the invention whose density isbetween those of the teal crystals and the green needles. Within secondsof the addition the teal crystals (A in FIG. 2B) floated to the liquidsurface and the green needles (B in FIG. 2B) sank. The needles wereremoved and the procedure was repeated to ensure the purity of thedesired top layer. The purified teal crystals were then collected. Asingle crystal X-ray structure as well as the PXRD pattern of the bulksample (FIG. 2A) confirmed that the desired pure product (5) had beenisolated. Powder X-ray diffraction (PXRD) patterns were recorded with aRigaku XDS 2000 diffractometer using nickel-filtered Cu Kα radiation(λ=1.5418 Å). Single crystals were mounted on a BRUKER APEX2 V2.1-0diffractometer. ¹H NMR and ¹³C NMR measurements were done on a VarianInova 500 spectrometer at 500 MHz and 125 Mhz, respectively. Elementalanalyses were conducted by Atlantic Microlabs of Norcross, Ga.

The particular 1:5 (v:v) DMSO:CH₂BrCl (liquid separation medium) usedwas initially determined pursuant to another embodiment of the inventionby placing an amount of the synthesized solid mixture comprised of MOFmaterial (5) and the second phase of crystalline green needles in afirst or parent liquid separation medium comprised of pure CH₂BrCl.Then, DMSO (as the second liquid separation medium of lower density thanthe CH₂BrCl liquid) was added incrementally until separation of thedesired pure MOF product (5) from the second phase of crystalline greenneedles occurs as a result of density differences therebtween. Thedensity of the collective separation liquid (i.e. the 1:5 (v:v)DMSO:CH₂BrCl separation medium) thereby was adjusted to lie betweenthose of the wanted pure MOF product (5) and the second phase ofcrystalline green needles to achieve separation and purification of thepure MOF product (5). The CH₂BrCl was used as the first or parentstarting solvent for this example (and the other examples set forth)below because of its high density (1.99 g/cm³) relative to most MOFs.

For verification, the densities of material 5 and its impurity weredetermined via pycnometry and found to be 1.28 and 1.94 g/cm³,respectively. The density of the solvent mixture was 1.82 g/cm³.

EXAMPLE 2

A new doubly-interwoven, pillared-paddlewheel⁸ MOF, Zn₂(NDC)₂(diQuNI)(6, yellow crystals), was synthesized by reacting 2 (FIG. 1), 3 (FIG.1), and Zn(NO₃)₂.6H₂O in diethylformamide (DEF) as described below. Thecrude product, however, was contaminated with a white crystallinematerial. MOF 6 was purified similarly to MOF 5 in Example 1, but with aliquid separation medium of 2:5 (v:v) DMF:CH₂BrCl. The desiredmixed-ligand compound floated while the contaminant sank. PXRD plots forboth fractions are shown in FIG. 3.

The particular 2:5 (v:v) DMF:CH₂BrCl (liquid separation medium) used wasinitially determined pursuant to the invention using the method likethat described in Example 1 with the difference being that DMF was addedto the pure CH₂BrCl, instead of DMSO, until separation of the MOF 6 andcontaminant occurred.

The structure of MOF 6 was established by single-crystal X-raymeasurements. ¹H NMR of an acid-dissolved sample of the contaminantestablished that it contained NDC but not diQuNI; PXRD data areconsistent with formation of an NDC-based cubic MOF or MOFs.⁹

For example, X-ray quality single crystals of MOF 6 were obtained uponheating Zn(NO₃)₂.6H₂O (15 mg, 0.05 mmol), H₂NDC (10 mg, 0.05 mmol) anddiQuNI (6 mg, 0.01 mmol) in 5 ml DEF at 80° C. for 48 hours. Brightyellow crystals were picked from the crude mixture with whitecrystalline powder for single crystal analysis. Single crystal X-raydiffraction: Single crystals were mounted on a BRUKER APEX2 V2.1-0diffractometer equipped with a graphite-monochromated MoKa (λ=0.71073 Å)radiation source in a cold nitrogen stream. All crystallographic datawere corrected for Lorentz and polarization effects (SAINT). Thestructures were solved by direct methods and refined by the full-matrixleast-squares method on F² with appropriate software implemented in theSHELXTL program package. All the non-hydrogen atoms were refinedanisotropically. Hydrogen atoms were added at their geometrically idealpositions. Most of the DMF solvent molecules are severely disordered,which hindered satisfactory development of the model; therefore, theSQUEEZE routine (PLATON) was applied to remove the contributions ofelectron density from disordered solvent molecules. The outputs from theSQUEEZE calculations are attached to the CIF file. After purification,isolated yield: 8 mg (30% yield based on Zn). Anal. calcd. for 6.5H₂O,C₅₆H₃₃N₄O_(14.5)Zn₂: C, 59.80; H, 2.96; N, 4.98. Found: C, 59.41; H,2.88; N, 5.28.

Synthesis of 3 (diQuNI): 1,4,5,8-naphthalenetetracarboxydianhydride (400mg, 1.49 mmol), 5-aminoquinoline (472 mg, 3.27 mmol), and 40 ml pyridinewere combined in a 100 ml 2-neck round bottom flask and heated to refluxovernight. After cooling, the solid was isolated by filtration andwashed with acetone and hexanes and allowed to dry in air. Isolatedyield: 279 mg, 36%. ¹N NMR (TFA-d): δ 9.16 (d, J=5.0 Hz, 2H), 9.04 (d,J=9.0 Hz, 2H), 8.98 (s, 4H), 8.49 (d, J=9.0 Hz, 2H), 8.35 (t, J=9.0 Hz,2H), 8.12 (d, J=8.0 Hz, 2H), 8.07 (t, J=8.0 Hz, 2H). MALDI-TOF MS: obs521.98; calcd [M+H]⁺521.49. Anal. calcd. for 3, C₃₂H₁₆N₄O₄: C, 73.84; H,3.10; N, 10.76. Found: C, 72.98; H, 3.34; N, 11.10.

EXAMPLE 3

IRMOF-10 (7 a, non-catenated structure)⁹ was synthesized utilizing 4,essentially as described by Yaghi et al.⁹, the teachings of which areincorporated herein by reference, except that DMF replaced DEF assolvent (IRMOF means isoreticulare MOF). As is often the case in MOFsyntheses, this seemingly minor change had significant consequences: 7 awas contaminated with substantial amounts of IRMOF-9 (7 b), the two-foldinterwoven analogue of 7 a. The mixture was separated by using a 4:5:26(v:v:v) solution (liquid separation medium) of CH₂Cl₂:CHCl₃:CH₂BrCl. Inthis solution, IRMOF-10 (A′ in FIG. 4B) floated as a separate layerwhile IRMOF-9 (B′ in FIG. 4B) sank as a separate layer. A single-crystalX-ray structure for 7 a has not been reported. The PXRD of the sample isshown in FIG. 4A. Finally, independently synthesized, pure samples of 7a and 7 b were intentionally combined and then successfullydensity-separated.

The particular 4:5:26 (v:v:v) solution (liquid separation medium) ofCH₂Cl₂:CHCl₃:CH₂BrCl used was initially determined pursuant to theinvention using the method like that described in Example 1 with thedifference being that CH₂Cl₂ and CHCl₃ were added to the pure CH₂BrClCH₂ClBr:CH₃Cl, instead of DMSO, until separation of the mixtureoccurred.

EXAMPLE 4

A Zn₂(bpdc)₂(L).10DMF.8H₂O MOF material was prepared in a vial byintroducing Zn(NO₃)₂ 6H₂O (12 mg, 0.04 mmol), H₂bpdc (7.2 mg, 0.03 mmol)and L (34 mg, 0.05 mmol) with DMF, 6 mL) (see FIG. 5) as described inCho et al., “A metal-organic framework material that functions as anenantioselective catalyst for olefin epoxidation”, ChemicalCommunications, (Cambridge, United Kingdom) (2006), 24, 2563-265, theteachings of which are incorporated herein by reference, with theexception that Zn-salen was used instead of Mn-salen. The vial wascapped and heated to 80° C. in an oil bath for one week, over which timebrown blocked shape crystals slowly formed.

The cubic non-active MOF impurities were separated from thecatalytically active MOF by suspending the solid mixture in 4:2:4(v:v:v) solution (liquid separation medium) of CH₂ClBr:CH₃Cl:DMF in aseparation flask pursuant to the invention, whereby the catalyticallyactive MOF floated to the top and the inactive MOF impurities sank tothe bottom of the separation flask.

The particular 4:2:4 (v:v:v) solution (liquid separation medium) ofCH₂ClBr:CH₃Cl:DMF used was initially determined pursuant to theinvention using the method like that described in Example 1 with thedifference being that CH₂ClBr and CH₃Cl were added to the pure DMF untilseparation of the mixture occurred.

EXAMPLE 5

Two MOF materials were synthesized from1,12-dihydroxycarbonyl-1,12-dicarba-closo-dodecaborane (1) (p-CDCH₂).Compound 1 and cobalt II salts were used to synthesize two newcoordination polymer materials by varying the reaction solvent andtemperature conditions as described by O. K. Farha et al., J. Am. Chem.Soc. 2007, 129, 12680, the teachings of which are incorporated herein byreference. A solid mixture of crystalline first MOF and crystallinesecond MOF with the different morphologies (block-like versusmicrocrystalline rods, respectively) were isolated from one another byplacing a solid mixture thereof in chloroform whose density is betweenthose of the first and second MOF's, whereby the first MOF floated tothe top and the second MOF sank to the bottom of the separation flask.

Although the present invention has been described with respect tocertain embodiments, those skilled in the art will appreciate thatchanges and modifications can be made thereto within the scope of theinvention as set forth in the appended claims.

References which are incorporated herein by reference:

-   1. Recent reviews: (a) Collins, D. J.; Zhou, H-C. J. Mat. Chem.    2007, 17, 3154-3160. (b) Rowsell, J. L. C.; Yaghi, O. M. Micro. and    Meso. Mat. 2004, 73, 3-14. (c) James, S. L. Chem. Soc. Rev. 2003,    32, 276-288.-   2. See, for example: (a) Nouar, F.; Eubank, J. F.; Bousquet, T.;    Wojtas, L.; Zaworotko, M. J.; Eddaoudi, M. J. Am. Chem. Soc. 2008,    130, 1833-1835. (b) Chen, B.; Ockwig, N. W.; Millard, A. R.;    Contreras, D. S.; Yaghi, O. M. Angew. Chem. Int. Ed. 2005, 44,    4745-4749. (c) Dinca, M.; Dailly, A.; Liu, Y.; Brown, C. M.;    Neumann, D. A.; Long, J. R. J. Am. Chem. Soc. 2006, 128,    16876-16883. (d) Bradshaw, D.; Claridge, J. B.; Cussen, E. J.;    Prior, T. J.; Rosseinsky, M. J. Acc. Chem. Res. 2005, 38,    273-282. (e) Kitagawa, S.; Kitaura, R.; Noro S. Angew. Chem., Int.    Ed. 2004, 43, 2334-2375. (f) Latroche, M.; Surblé, S.; Serre, C.;    Mellot-Draznieks, C.; Llewellyn, P. L.; Lee, H.; Chang, J.;    Jhung, S. H.; Férey, G. Angew. Chem., Int. Ed. 2006, 45,    8227-8231. (g) Mulfort, K. L.; Hupp, J. T. J. Am. Chem. Soc. 2007,    129, 9604-9605. (h) Farha, 0. K.; Spokoyny, A. M.; Mulfort, K. L.;    Hawthorne, M. F.; Mirkin, C. A.; Hupp, J. T. J. Am. Chem. Soc. 2007,    129, 12680.-   3. See, for example: (a) Lee, E. Y.; Jang, S. Y.; Suh, M. P. J. Am.    Chem. Soc. 2005, 127, 6374-6381. (b) Dinca, M.; Long, J. R. J. Am.    Chem. Soc. 2005, 127, 9376-9377. (c) Snurr, R. Q.; Hupp, J. T.;    Nguyen, S. T. AIChE, 2004, 50, 1090-1095.-   4. See, for example: (a) Cho, S. -H.; Ma, B.-Q.; Nguyen, S. T.;    Hupp, J. T.; Albrecht-Schmitt, T. E. Chem. Commun. 2006,    2563-2565. (b) Wu, C. D.; Hu, A.; Zhang, L.; Lin, W. J. Am. Chem.    Soc. 2005, 127, 8940-8941. (c) Gomez-Lor, B.; Gutierrez-Puebla, E.;    Iglesias, M.; Monge, M. A.; Ruiz-Valero, C.; Snejko, N. Chem. Mater.    2005, 17, 2568-2573. (d) Kitaura, R.; Onoyama, G.; Sakamoto, H.;    Matsuda, R.; Noro, S. I.; Kitagawa, S. Angew. Chem., Int. Ed. 2004,    43, 2684-2687.-   5. See, for example: a) Hafizovic, J.; Bjorgen, M.; Olsbye, U.;    Dietzel, P. D. C.; Bordiga, S.; Prestipino, C.; Lamberti, C.;    Lillerud, K. P. J. Am. Chem. Soc. 2007, 129, 3612-3620. b) Ma, S.;    Sun, D.; Ambrogio, M.; Fillinger, J. A.; Parkin, S.; Zhou, H.-C. J.    Am. Chem. Soc., 2007, 129, 1858-1859.-   6. Sudik, A. C.; Millward, A. R.; Ockwig, N. W.; Côté, A. P.; Kim,    J.; Yaghi, O. M. J. Am. Chem. Soc., 2005, 127, 7110-7118.-   7. Sun, D.; Ma, S.; Ke, Y.; Collins, D. J.; Zhou, H. J. Am. Chem.    Soc. 2006, 128, 3896-3897.-   8. Ma, B., Mulfort; K. L., Hupp; J. T., Inorgan. Chem., 2005, 44,    4912-4914.-   9. Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak, D; Wachter, J; OKeefe, M;    Yaghi, O. M., Science, 2002, 295, 469-72.-   10. Yaghi, M. O. et al. U.S. Pat. No. 6,930,193

1. A method of purification of a solid mixture comprising ametal-organic framework material and a second material, comprisingdisposing the solid mixture in a liquid separation medium having adensity that lies between those of the wanted MOF material and theunwanted material, whereby the solid mixture separates by densitydifferences into a fraction of wanted MOF material and a fraction ofunwanted material.
 2. The method of claim 1 including isolating acrystalline MOF material from a mixture containing a second materialcomprising the same organic-strut and/or metal-ion building blocks. 3.The method of claim 1 including separating of a mixed-organic strut MOFmaterial from a second MOF material containing only a single type oforganic strut.
 4. The method of claim 1 including separating anon-interpenetrating MOF material from an otherwise identical materialconsisting of catenated networks.
 5. The method of claim 1 including aseparating different MOF morphologies.
 6. The method of claim 1including a separating a catalytically active MOF material and anon-active species of the MOF material.
 7. A method of purification of asolid mixture of a metal-organic framework (MOF) material and a secondmaterial, comprising disposing the solid mixture containing a MOFmaterial to be isolated and the second material in a first liquidseparation medium having a density greater than that of the MOF materialand introducing a second liquid separation medium that is miscible inthe first liquid separation medium and having a density less than thatof the first liquid separation medium in a manner to adjust thecollective density of the liquid separation medium so that it liesbetween those of the MOF material and the second material, whereby thesolid mixture separates into a floating fraction of the MOF material anda sinking fraction of the second material.
 8. The method of claim 7including isolating a crystalline MOF material from a mixture containinga second material comprising the same organic-strut and/or metal-ionbuilding blocks.
 9. The method of claim 7 including separating of amixed-organic strut MOF material from a second MOF material containingonly a single type of organic strut.
 10. The method of claim 7 includingseparating a non-interpenetrating MOF material from an otherwiseidentical material consisting of catenated networks.
 11. The method ofclaim 7 including a separating different MOF morphologies.
 12. Themethod of claim 7 including a separating a catalytically active MOFmaterial and a non-active species of the MOF material.